1. Field of the Invention
One embodiment of the present invention relates to a lighting device including a light-emitting member which exhibits electroluminescence.
2. Description of the Related Art
As a next-generation lighting device, a lighting device using an electroluminescent material has attracted attention because it is estimated to have higher emission efficiency than filament bulbs or fluorescent bulbs. A thin film of an electroluminescent material can be formed to a thickness of 1 μm or less by evaporation or coating. Further, the structure of such a lighting device has been devised; for example, some inventions disclose a lighting device using an electroluminescent material in which the luminance is kept constant even when the area of the lighting device is increased (for example, see Patent Document 1).
Further, in order to reduce the load on an electroluminescent panel, a lighting device is disclosed in which an electroluminescent panel is formed into a ring shape to have an opening in its center (for example, see Patent Document 2). This lighting device has a structure in which a terminal is led from an electrode of the electroluminescent panel to the inner of the center opening so that the led terminal is connected to a driver circuit provided in a supporting member attached to the center.
In the lighting device having such a structure, a metal plate, a conductive wire, or the like needs to be attached to a thin film electrode by soldering or the like in order to lead the terminal of the thin film electrode of the electroluminescent panel to the inner of the center opening.
However, even when the metal plate or the conductive wire is attached to the thin film electrode, the thin film electrode has a problem in that it has low adhesion and thus is easily separated from a substrate. There is also a problem in that the thin film electrode and the lead terminal such as the metal plate or the conductive wire need to be additionally provided, leading to an increase in the number of components and a complicated structure. As a result, reduction in the thickness of a lighting device is prevented from being achieved even though an electroluminescent element is a thin film.